Channel 4 has been accused of letting people who use subtitles down after its programmes were the worst affected by an “unprecedented” issue.

The broadcaster breached its broadcasting licence amid a prolonged outage on their subtitles, audio description and signing, an Ofcom investigation has found.

Millions of Freesat viewers who rely on accessible services were unable to watch their programmes in September of last year during the issue.

The broadcaster was further reprimanded for failing to communicate with its viewers who rely on subtitles, regarding the nearly two-month-long issue.

The outage followed a “catastrophic failure” at a broadcast centre run by Red Bee Media. Fire suppressant gas was released and caused a loud shockwave, damaging many servers beyond repair.

Channel 4 took nearly three weeks before broadcasting on-air advice and information about the outage. This left people without access to online information with no knowledge of the scale of the issue nor the work to repair it.

Several broadcasters were affected but Channel 4 was the worst hit with the Ofcom investigation finding that its response was not “sufficiently resilient” after its backup subtitling system also failed.

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Channel 4 took eight weeks to restore subtitles – twice the time needed for Sky, Freeview, Youview and Virgin Media to reintroduce them.

The services, which are essential to many viewers who are deaf, have hearing loss , are blind or partially sighted, were down from September 25, 2021 until November 19, 2021.

As a result, Channel 4 fell short of annual quota to subtitle 90 per cent of its programmes on Freesat. Only 85.41% of programmes were subtitles, breaching its licence conditions.

Ofcom received around 500 complaints during this period and launched an investigation at the start of this year.

Channel 4 did not provide any information about the cause of the outage or steps being taken to resolve it for 12 days following the incident, the investigation found.

The broadcaster must now report to Ofcom by the end of this year on the steps it has taken to ensure greater resilience of its access services and how it is improving accessibility.

Kevin Bakhurst, Ofcom’s Group Director for Broadcasting, said: “When things go wrong, broadcasters must have plans in place to restore important services, but also to let audiences know what they can expect.

“By failing to do this, Channel 4 let down people who use subtitles, signing or audio description to enjoy programmes.”

"There are a number of lessons for broadcasters to learn from this incident. We've told them they must improve and test their back-up plans and infrastructure to minimise the risk of such a disruptive outage happening again."

A Channel 4 spokesperson said: “Channel 4 is very disappointed with Ofcom’s decision and will review its findings carefully. We would like to apologise once again to our audiences for the disruption to our access services following the catastrophic incident last September and since then we have implemented a number of new systems and processes to avoid a serious incident in the future.”